Method of making dielectric stencils



June 20, 1950 A, R, lNDsAY 2,512,348

METHOD 0F MAKING DIELECTRIC STENCILS Filed Sept. 23,'1948 Y v f ,l iM/2%@ j j.

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INVENTOR.

Patented June 20, 1950 UNITED STATES PATENT OFFICE METHOD oF MAKING DIELECTRIC s'rENcrLs Allen Bi. Lindsay, Cleveland` Heights, Ohio Application September 23, 1948, Serial No, 50,758

Claims. l

This invention relates to a method of making dielectric stencils such as the stencil disclosed in my co-pending application Serial No. 503757, led September 23, 1948.

These stencils are used in conjunction with electrical etching tools for marking metallic articles such as tools, machines and various parts thereof.

The stencil is formed from a composite sheet 'of material and has the desired character im pressed into the bottom thereof. In use the stencil is secured to a suitable etching tool and brought into contact with the article to be marked. The impression defining the character is then filled with a suitable electrolyte which is generally contained in a reservoir in the tool. An electric current is then passed through the electrolyte and into the article, the stencil holder er tool acting as the cathode and the article constituting the anode. One form ofsuch an etch.- ing tool is shown in my co-pending application Serial No. 631,401, led November 28, 1945, which has matured into Patent No. 2,498,129 Feb. 21, 1950. The actual etching time is very short, ju-st a few seconds, so that a large number of articles can be marked in a short time. Asthe stencil is repeatedly brought into engagement with articles to be marked, which very often have a rough surface, it is subjected to mechanical 'abrasion which eventually wears out the stencil so, that it has to be replaced with a new stencil.

The principal object of this invention is to provide a method of making dielectric stencils, for use with electrical etching devices, which are so constructed that they will resist mechanical abrasion and will have a much longer life than previously known stencils of this character.

' Another object of the invention is to provide a method of making stencils which can be repeatedly used many times and. will produce av clear cut well defined mark on a metallic article.

'\ lAnother object of the invention is to provide -a simple, economical and efficient method of Vvmaking stencils having the aforesaid character 'or character 5.

Fig. 4 is an enlarged fragmentary section through the. paper used in making the stencil;

Fig. 5 is a detail sectional view showing one way of applying a thin film of wax to one side of the paper;

Fig, 6 is an enlarged fragmentary section showing a thin lm of wax applied to one side of the paper;

Fig. "7' is a view similar to Fig. 6 showing a thin film of buna rubber applied to the wax film;

Fig. 8 is an enlarged sectional View showing the manner of impressing a character into the composite sheet of paper, wax and buna rubber; and

Fig.-9 is a detail view showing one way of curing and vulcanizing the lm of buna rubber around the character.

Referring now to the drawings by reference characters, the numeral l indicates generally a squarerectangular or any otherdesired shape,v

depending on the size and shape of the mark desired and on the type of etching tool with which the stencil is used. Also the stencil need not be cup-shaped as shown. In some instances it may be .desirable to make the stencil in the form of a Kflat sheet.A

` `The stencil is made from a composite sheet of material 'l which is first molded into shape, after which the desired mark or character .5 is impressed into the bottom wall 2 thereof by a sultable die.

' The material l comprises a treated paper sheet `il, a thin film of wax 9 and a thin film It of high Ytemperature paran and buna rubber, all firmly bonded together into a composite sheet. lThe paper 8 is preferably uncoated long fibre paper having extremely open tissues so that it is very pervious and will allow electrolyte to readily pass through.

In making the stencil I first treat the paper 8 with chlorinated oil which seals the hygroscopic fibres and bonds them together. Then I apply the thin film of wax 9 to one side of the paper. In applying the film 9 I first dissolve paraffin and an animal wax in a suitable solvent, such as ether, which has been heated to approximately Then I pass the paper 8 over a chilled roller II which dips into the Wax solution I2 in the container I3. As the paper 8 passes over the chilled roller II and through the solution I2 the roller II cools the paper and causes the thin nlm 9 to freeze onto the paper and firmly bond therewith. Next I spray an emulsion of high temperature paraffin and buna rubber onto the film 9 with a hot blast 'air gun I4. As the emulsion comes into contact with the Wax lm it solidiiies into the thin film of paraffin and buna I 0.

The stencil I is then molded from the composite sheet 1, with the films 9 and I0 on the outside of the stencil. After the stencil has been molded to form, I impress the desired mark or character into the bottom thereof with a suitable die I5 as indicated in Fig. 8. As the die I5 is forced into the material it ruptures and displaces the films 9 and I0 and forms the raised border 6 around the character. The die also compresses the paper 8 thereunder` which forces all Wax and oil out of the compressed portion, leaving bare fibre through which electrolyte can readily pass. After the character has been impressed I ll the impression with electrolyte and then pass an electric current through the electroylte. This lgenerates enough heat to cure and vulcanize the film of buna rubber around the mark which gives the buna nlm high mechanical strength and provides a tough tenacious lm which resists mechanical abrasion. The simplest Wayto cure and vulcanize the buna film is to secure the stencil to an etching tool I6 and use it once or twice found that a stencil made according to my method E can be used 1900 times before it is worn beyond a desirable Working point. Other known stencils when used in the same manner averaged only times.

It is to be understood that I am not limited to? the specic method shown and described herein as various modifications can be made thereto within the. scope ofthe appended claims.

Having thus described my invention, I claim:

'1. The method of making a dielectric stencil comprising, applying a thin iilm of animal Wax to one side of a sheet of uncoated long bre open tissue paper, applying a thin nlm of high temperature paraffin and buna rubber to the Wax film, molding a stencil from the composite' sheet thus formed, impressing a character into said sheet by forcing a die thereinto in such a manner as to rupture and displace the wax film and the buna rubber film, filling said character with electrolyte, and then passing an electric current through said electrolyte thereby generating suf- 1 cient heat to vulcanize the buna rubber iilm surrounding said character.

`2. The method of making a dielectric stencil comprising treating a sheet of uncoated long fibre open tissue paper with chlorinated oil to seal the hygroscopic fibres and bind them together, coating one side of said sheet With a film containing synthetic rubber, molding a stencil from said coated sheet, impressing a character into said' sheet in such a manner as to rupture and displace said film, filling said character with electrolyte, and then passing an electric current; through said electrolyte thereby generating sum cient heat to vulcanize the lm surrounding said; character.

3. The method of making a dielectric stencil', comprising, treating a sheet of uncoated longi iibre open tissue paper with chlorinated oil toy seal the hygroscopic fibres and bind them to gether, coating one side of said sheet with a film containing animal Wax, applying a second film which contains synthetic rubber to said rst mentioned iilm, lmolding a stencil from the composite sheet thus `formed, impressing a character into said sheet by forcing a die thereinto in such a manner as to rupture and displace the Wax lm and the buna rubber film, filling said character with electrolyte, and then passing an electric current through said electrolyte thereby generating suicient heat to vulcanize the buna rubber lm surrounding said character.

4. The method of making a dielectric stencil comprising, coating one side of a sheet of uncoated long fibre open tissue paper With a nlm containing buna rubber, molding a stencil from said coated sheet, impressing a character into said sheet in such a manner as to rupture and displace said film, lling said character with electrolyte, and then passing an electric current through said electrolyte thereby generating suiiicient heat to vulcanize the iilm surrounding said character.

5. The method of making a dielectric stencil comprising, treating a sheet of uncoated long bre open tissue paper with chlorinated oil to seal the hygroscopic bres and bind them together, freezing a solution of parafiin and animal Wax into a film on one side of said paper sheet, spraying an emulsion containing high temperature paraiin and buna rubber onto said film, said emulsion solidifying into a second film which -is firmly bonded to said first mentioned lm, molding a stencil from the composite sheet thus formed, impressing a character into said sheet .by forcing av die thereinto in such a manner as REFERENCES CITED The following references are of record in the fiie of this patent:

UNITED STATES PATENTS Number Name Date 1,293,983 'Thomas Feb. 11, 1919 1,371,157 Gestetner Mar. 8, 1921 1,633,072 Davis June 21, 1927 2,140,506 Canning Dec. 20,1938 2,405,508

Lindsay Aug. 6, `:194:6 

4. THE METHOD OF MAKING A DIELECTRIC STENCIL COMPRISING COATING ONE SIDE OF A SHEET OF UNCOATED LONG FIBRE OPEN TISSUE PAPER WITH A FILM CONTAINING BUNA RUBBER, MOLDING A STENCIL FROM SAID COATED SHEET, IMPRESSING A CHARACTER INTO SAID SHEET IN SUCH A MANNER AS TO RUPTURE AND DISPLACE SAID FILM FILLING SAID CHARACTER WITH ELECTROYTE, AND THEN PASSING AN ELECTRIC CURRENT THROUGH SAID ELECTROYLTE THEREBY GENERATING SUFFICIENT HEAT TO VULCANIZE THE FILM SURROUNDING SAID CHARACTER. 